Valve for breathing apparatus



Aug. 9, 1966 ss VALVE FOR BREATHING APPARATUS Filed July 9. 1963 2 Sheets-Sheet 1 h g Z 10 g /10c| Httovnegs 9, 1966 H. HESSE 3,265,062

VALVE FOR BREATHING APPARATUS Filed July 9, 1963 2 Sheets-Sheet 2 HOLsev Hesse United States Patent 3,265,062 VALVE FOR BREATNG APPARATUS Holger Hesse, kovtoftebakken 19, Copenhagen- Virum, Denmark Filed July 9. 1963, Ser. No. 293,675) Claims priority, application Germany, July 14, 1962, H 46,381 Claims. (Cl. 12829) The invention is concerned with a type of gas valve for breathing apparatus provided with a valve element that is adapted to be moved by gas pressure in a gas flow passage in such a way between two seats that, at a predetermined gas pressure, it will leave a normal seating position on the upstream seat nearer to the source of gas flow thereby opening said flow passage and, at a predetermined higher gas pressure, it will close said flow passage in a final seating position on the downstream seat remote from said source. Valves of this type are adapted for use in artificial breathing apparatus for life-saving purposes and in narcosis apparatus. Specifically such valve should be adapted for such application in life-saving apparatus that the return flow of breathing air expired by the patient to the source of fresh air supply is rendered impossible, such expiration air instead being diverted to atmosphere.

In gas valves previously used in breathing and narcosis apparatus of the type here in question the valve ele ment is returned to the normal seat-ing position by gravity or by spring means urging the valve to close the gas supply passage against any gas flow pressure lower than a predetermined valve opening pressure. Any gas flow pressure amounting to or greater than said valve opening pressure will overcome the resistance offered by gravity or spring action and, as long as gas flow pressure is below a predetermined cut-off pressure, the valve element will not close said downstream seat and accordingly gas will flow from the source through said upstream seat past said valve element and through said downstream seat, the flow passage thus being open. Upon the application of pressure above said cut-01f pressure, such as the pressure surge provided by compressing a pumping ball or the like forming part of the breathing of narcosis apparatus, the valve element will be forced against said downstream seat thus closing the air flow passage therethrough as long as the pressure supplied will be sufiicient to counteract the force due to gravity or spring action tending to return the valve element to the normal seating position on said upstream seat.

Gravity-operated valves are working dependent on their position and this position-sensitivity is a serious disadvantage which restricts the use of such valves to stationary narcosis apparatus, leaving the problem of portable lifesaving and narcosis equipment unsolved. While a biasing spring is not position-sensitive it requires a very high degree of adjustment in respect to the critical valve opening and cut-01f pressures. The adjustment of the spring being critical, it is obviou that already a Very slight action exerted on the spring during disassembling, cleaning and assembling of the valve will definitely change the characteristics of the valve.

A further important disadvantage inherent in springs when used in valves of the type here in question is caused by the fact that the resistance offered by the spring to the shift of the valve element under the action of gas flow pressure is maximal in the cut-olf position of the valve element, the gas pressure being required to be maintained at the initial cut-off value in order that the state of cut-oil is to be maintained. This condi tion may be adverse in some applications where it may be desirable to maintain the state of cut-off after momen- 3,265,662 Patented August 9, 1966 taneous appearance of the cut-off pressure in spite of the fact that the pressure immediately afterwards falls to a lower value.

All these disadvantages of conventional gravity or spring actuated gas valves are avoided according to the invention by a construction in which the valve element is held in its normal position by at least one magnet and is held in an intermediate position in which said flow passage is opened by said magnet or at least one of several said magnets.

Obviously magnetic valve element returning means are entirely independent of the position in which they are used. They permit a very simple construction enabling the valve to be readily disassembled, cleaned and reassembled, these steps not involving any risk of misadjustment which alters the characteristics of the valve. Finally the magnetic holding means exert a biasing force decreasing with the distance from the magnet pole which means that once the valve element has been shifted by gas pressure against the action of the magnetic means from the normal position to the intermediate position or from the intermediate position to the final cut-off position a pressure lower than the critical shifting pres sure will be suflicient to hold the valve element in the position achieved.

Preferably the valve element is in the form of a disc which by means of the magnet or magnets is held in the normal position against said upstream seat and by means of the magnet or at least one of several magnets is held inclined in said intermediate position in partial contact with said upstream seat. In its oblique intermediate position the valve element is suitably in partial contact with both seats, contact of the valve element with either seat preferably being made at diametrically opposed points on respectively opposite sides of the element.

In breathing apparatus and the like the flow passage may be branched between the two seats, the valve element in its intermediate position opening a connection from the source of gas to both branches and in the final cut-01f position closing one of the branches.

The invention will be explained in greater detail by reference to the attached drawings in which FIGURE 1 shows an apparatus arrangement for administering narcosis gas to a patient. FIGURE 2 shows part of an apparatus arrangement for supplying an air-oxygen mixture for life saving purposes. FIGURES 3 and 4 are sectional views of two embodiments of the novel valve of the invention adapted to be used, for example, in the apparatus arrangements shown in FIGURES 1 and 2.

The apparatus arrangements shown in FIGURES l and 2 are here described for the purpose of providing a background to the subsequent description of the construction and operation of the valve according to the invention which, although being of general utility, has been primarily designed for the purpose of improving the performance of apparatus arrangements of the type shown in FIGURES 1 and 2.

In FIGURE 1; reference numeral 1 designates a medical gas cylinder from which gas, such as narcosis gas, is supplied via an adjustable pressure reducing valve 2 comprising a pressure gauge and flow meter 3 indicating the gas flow in liters per minute, the gas flowing from said flow meter to a valve unit 5 and from this to a breathing mask 8 adapted to be placed over the mouth and nose of the patient. In conventional apparatus of this kind valve unit 5 usually comprises a spring biased valve element controlling the direction of gas flow in dependence on the flow pressure conditions. In a conduit branchedoff from the gas flow conduit between said flow meter 3 and valve unit 5 there is attached a breathing bag 4 of relaxedly collapsed rubber.

During use, gas is supplied, for example, at a rate of 10 liters per minute. Irrespective of its construction the valve unit is so adjusted that a valve element, here schematically shown as a floating disk 6, is biasedconventionally by spring action or gravityagainst an upstream seat to close the inlet conduit 11 at any pressure lower than that corresponding to the adjusted rate of gas flow. Thus the gas supplied will not flow past the valve element 6 but enter into bag 4 which thus is inflated. With a certain degree of inflation a state of equilibrium will be obtained between, on the one hand, the back-pressure force exerted by the expanded bag walls and, on the other hand, the biasing force acting on the valve element 6 this state of equilibrium being maintained during steady flow of gas from the source by corresponding discharge of gas past the slightly unseated valve element 6. The valve unit 5 forms a three-way conduit with one branch 11 forming the inlet, one branch connected to the breathing mask 8 and one branch 7 leading to atmosphere. In the above defined state of equilibrium the gas flow past valve element 6 will be substantially drained to atmosphere. In practice the rate of gas flow will be chosen in accordance with calculated supply requirements for e.g. a sustained state of narcosis. Thus, prior to complete inflation of the bag, the anesthetist will compress the bag to cause a surge of gas under increased pressure to flow towards valve element 6. The biasing pressure acting thereon in the opposite direction is so adjusted as to be fully overcome by any such pressure surge due to bag compression and the valve element is thus forced back against a downstream seat to close said branch leading to atmosphere. All of the gas supplied by compression of the bag will thus be forced to pass through the breathing mask 8 into the lungs of the patient. As soon as the bag is released from compression the valve element 6 will return to its biased position against the upstream seat and after renewed inflation of the bag the process may be repeated.

Gas expired from the lungs of the patient may pass from the breathing mask 8 into the outlet branch 7 but is prevented from flowing into the bag 4 by the check valve action of the valve element 6. Obviously, in a modification of the arrangement the valve unit may be made to operate Without said check-valve effect the connection between the inlet branch and the breathing mask branch in this case being permanently open and the valve element and double seat structure being provided in the outlet branch. In such a modified arrangement of the valve unit the outlet will be closed by any gas pressure surge due to compression of the bag, the gas thus being forced to penetrate into the lungs of the patient. Gas expired from the lungs of the patient as well as equilibrium gas flow from the gas source will be dicharged past the slightly unseated valve element in the outlet branch of the valve unit.

The apparatus shown in FIG. 2 is a life-saving equipment adapted to be connected to a cylinder, gauge and flow meter arrangemnt similar to that shown in FIG. 1, the cylinder in this case containing oxygen. Serially inserted between the flow meter and the valve unit 5 is a normally resiliently expanded, compressible ball 4a which may be of the type in which quick resilient expansion in combination with low compression resistance is obtained by the use of a hollow body of foam rubber or the like covered by a readily flexible film or coat of an impervious material. A check valve normally closing an opening leading to atmosphere is provided in a branch of the conduit leading from the flow meter to the inlet opening of ball 4a. Obviously, this arrangement permits supplying the patient either with pure oxygen from the cylinder, or with air sucked up through check valve 12 by the ball 4a resiliently expanding after compression or with an adjusted mixture of oxygen and air. The action of valve unit 5 is similar to that described in connection with FIG. 1.

It will be obvious that any valve construction to be used in a valve unit 5 of an apparatus as shown in FIGS. 1 and 2 must be designed to open a connection from the valve inlet 11 to both the breathing mask 3 and the outlet 7 when flow pressure is above a certain value which in the applications described corresponds to the adjusted steady supply flow from cylinder 1. Evidently at such pressure, valve element 6 must not be allowed to close the outlet 7 if uncontrolled penetration of gas into the lungs of the patient is to be avoided. Thus the valve construction must be such that valve element 6 is forced against the downstream seat to close the outlet only when by a deliberate action of the anesthetist or life saver the bag 4 or ball 41: is compressed for causing a pressure surge to pass through valve unit 5 and, due to the closing of the outlet, into the lungs of the patient. Assuming that valve element 6 is spring biased towards its inlet closing position the spring will be in its most tensioned state when during the occurrence of a pressure surge due to compression of the bag or ball the valve element is in its outlet closing position against the outlet or downstream seat. Thus, any transient lowering of the pressure due to momentaneous relaxation, inadvertent or deliberate, of bag or ball compression may allow the spring momentarily to overcome the reduced pressure and to cause the valve element to re-open the outlet. Under certain conditions this may be a serious disadvantage.

The valve construction according to the invention to be described now is free from this drawback and in addition is more sturdy and more easily disassembled, cleaned and assembled than any prior art valves of the type here in question.

The embodiment of a valve unit shown in FIG. 3 comprises a tubular housing 9 having a laterally extending connection 10a for attaching the breathing mask or the like. The inlet 11 extends through an inlet element 11a adapted to be connected to the pipe, tube or hose supplying the treating gas from a source, such as the combined cylinder, gauge, flow-meter and bag or ball arrangement shown in FIGS. 1 or 2. On its downstream face within housing 9 inlet element 11a is provided with an annular inlet or upstream valve seat 1117.

An outlet 7 in line with the inlet 11 extends axially through an outlet element 13. Both the inlet element 11a and the outlet element 13 are inserted into the housmg 9 1D. any suitable Way, such as by threads 15 and 16 respectively, permitting ready disassembly and reassembly of the parts. The outlet element 13 is provided with an axial tubular extension extending towards and termmatmg short of seat 11b in a corresponding annular outlet or downstream seat 14. Extension 13a has reduced outer diameter, the annular space formed between housing 9 and extension communicating with the outlet passage 10 in connection 10a. Loosely inserted between seats 11b and 14 is a circular disk-sha ed valve element 17 of paramagnetic material. A magnet composed of three parts 19, 20 and 21 is provided in the inlet element 11a behind seat 11b in a position to hold disck 17 normally seated against seat 11b. Obviouslv the characteristics of the magnet will be chosen in con sideration of the holding force required for operating the valve in accordance with the principles outlined above. While disk 17 is held against seat 11/) at any gas flow pressure up to the adjusted steady flow pressure from cylinder 1, it will be partly unseated and shifted to an inclined intermediate position in partial contact with both seats (as shown in broken lines at 1712) at any gas flow lower than a predetermined actuating or surge pressure supplied, for example, by compression of bag 4 or ball 4a. Any such actuating or surge pressure will overcome the holding action of magnet 19, 2t 21 and shift disk 1'7 into complete contact with seat 14 to the broken line position in which outlet 7 is closed and a flow passage is open from inlet 11 to passage leading to the breathing mask.

As magnetic force decreases with increased distance from the magnet, disk 17 obviously will be held against seat 14 by a flow pressure lower than that required for shifting disk 17 from position 17b to position 17c.

It has been found advantageous to provide for a preferential direction of inclination of the disk 17 in the intermediate position between the two seats 11b and 14 by arranging the magnet or magnets so that the magnetic field is definitely asymmetrical in respect to disk 17. In the embodiment shown in FIG. 3 the magnet formed by parts 19, 20 and 21 asymmetrically acts on disk 17 due to the fact that leg 20 terminates at a greater distance from seat 111) than leg 19, the latter thus exerting a more powerful holding action causing disk 17 preferentially to assume the inclined intermediate position 17b shown. Obviously, an equivalent solution would be to make the length of leg 20 equal to that of leg 19 but instead to design leg 20 with a smaller cross-sectional area than leg 19 or even to combine shorter length and smaller crosssection. A suitably dimensioned, excentrically disposed single magnet may also be used to attract disk 17 with asymmetrical force. For the same purpose the pole ends of the magnet or magnets may be deformed. Further equivalent constructions will be readily apparent to the expert.

In the embodiment of FIG. 3 inlet 11 is shown to be excentrically disposed in relation to seat 11b, this construction eliminating the risk of a permanent jamming of disk 17 in the inclined position 17b due to excessive magnetic attraction exerted on the edge of disk 17 by the more powerful leg 19 exteriorly of seat 111:.

The embodiment of a valve unit shown in FIG. 4 is functionally similar to that shown in FIG. 3 but has the following additional and modified features.

Inlet 111 extends through inlet element 111a concentrically in relation to seat 11112. A cage 125 extends axially in a downstream direction from inlet element 111a Within housing 109, said cage 125 concentrically surrounding seat 111b in a way permitting disk 117 freely to move to respectively said intermediate and outlet closing positions but preventing it from being radially displaced during axial movement adjacent the inlet closing position. The cage 125 will thus hold disk 117 centered on seat 111b and will perform this action also upon disassembly of the inlet element, it being understood that in the absence of a similar feature in the embodiment of FIG. 3 disk 17 may be readily wiped off from the detached inlet element 11a, this accident evidently involving a severe risk in an emergency situation.

In the embodiment of FIG. 4 extension 113a of outlet element 113 extends into cage 125 which in the assembled state of the device thus surrounds downstream seat 114 as well as upstream seat 111b.

The embodiment according to FIG. 4 is fundamentally in conformity with that of FIG. 3 as far as the breathing mask connection 110a and the passage 110 therein is concerned.

The magnet 123 used in the embodiment according to FIG. 4 is a ring magnet disposed concentrically about inlet 111 behind seat 111b and having an air gap (not shown) at which the magnetic force is concentrated, the asymmetric magnetic action thus obtained causing the disk 117 preferentially to assume a certain inclined intermediate position.

When an apparatus of the type shown in FIGS. 1 and 2 is to be used in a poisoned atmosphere check valve means must be provided preventing the patient from inhaling poisoned air through the outlet 107. While an advantageous embodiment of such check valve means is shown here in connection with the valve unit according to FIG. 4 it is to be understood that, on the one hand, similar or other check valve means may be combined with any embodiment of the present valve unit d and that, on the other hand, the valve unit of FIG. 4 also without such check valve means completely embodies the present invention.

The specific check valve shown in FIG. 4 may be said to have fundamentally the same construction as the valve formed by seats HM; and 114 and disk 117. Thus the check valve comprises an upstream seat provided on the downstream end of outlet element 113 and surrounded by a cage 131 rearwardly extending from outlet element 113. A ring magnet 132 carried by the outlet element 113 and concentrically extending about outlet 107 is adapted to hold a disk shaped valve element 133 against seat 130. In all essential respects seat 130, cage 131, magnet 132 and disk 133 correspond to respectively seat 111b, cage 125, magnet 12.3 and disk 117. A downstream seat 134 is concentrically supported opposite seat 130 within cage 131 by means of an end sleeve 135 which is screwed at 136 onto the outlet element 113 and which is provided with axial outlet openings 137 communicating with the space within the cage 131.

In operation the check valve will not prevent expiration air from the lungs of the patient from flowing past disk 133, the magnetic biasing force being chosen in respect to this function. The check valve will not either prevent a steady gas flow from the supply from being discharged to atmosphere without undue penetration into the lungs of the patient. In other words, the check valve will in no way alter the Working conditions of the air or gas supply system but will effectively prevent contaminated or poisoned air from entering into the device.

The invention is not restricted to the specific embodiments shown and described but comprises all equivalent constructions.

What I claim is:

1. A gas inhalation valve comprising a gas flow conduit open at opposed ends, means at one of said ends for connecting said conduit to a source of gas under pressure, a magnetically responsive valve element, movable within said conduit between a pair of opposed upstream and downstream seats, means for establishing a gas flow from said source towards said valve at a first predetermined pressure, means for temporarily establishing gas flow at a second predetermined pressure higher than said first predetermined pressure, and magnetic means adapted, at gas flow pressures below said first predetermined pressure, to hold said valve element in inlet-closing seating contact with said upstream seat and, at gas flow pressures above said first predetermined pressure and below said' second predetermined pressure, to hold said valve element in partial, inlet-opening contact with said upstream seat, said magnetic means, at gas flow pressures above said second predetermined pressure, releasing said valve element for movement into seating contact with said downstream seat.

2. A gas inhalation valve comprising a gas flow conduit open at opposed ends, means at one of said ends for connecting said conduit to a source of gas under pressure, a magnetically responsive disk-shaped valve element movable within said conduit between a pair of opposed upstream and downstream seats, means for establishing a gas flow from said source towards said valve at a first predetermined pressure, means for temporarily establishing gas flow at a second predetermined pressure higher than that first predetermined pressure, and magnetic means adapted, at gas flow pressures below said first predetermined pressure, to hold said valve disk in inletclosing seating contact with said upstream seat and, at gas flow pressures above said first predetermined pressure and below said second predetermined pressure, to hold said valve disk in an oblique position in partial, inletopening contact with said upstream seat, said magnetic means, at gas flow pressures above said second predetermined pressure, releasing said valve disk for gas-flow induced movement into outlet-closing seating contact with said downstream seat.

3. The valve as claimed in claim 2 in which the valve disk in said oblique position is in partial, inlet and outlet opening contact with both said upstream and downstream seats.

4. The valve as claimed in claim 2 in which the valve disk is circular and in said oblique position is in contact with both seats at respectively diametrically opposed positions on its opposite faces.

5. A gas inhalation valve comprising a gas flow conduit open at opposed ends, means at one of said ends for connecting said conduit to a source of gas under pressure, a magnetically responsive valve element movable within said gas conduit between a pair of opposed upstream and, downstream seats, means for establishing a gas flow from said source towards said valve at a first predetermined pressure, means for temporarily establishing gas flow at a higher second pressure, magnetic means adapted, at gas flow pressures below said first predetermined pressure, to hold said valve element in full seating contact with said upstream seat and, at gas flow pressures above said first predetermined pressure and below said second predetermined pressure, to hold said valve element in an obliquely unseated position in partial contact with both said upstream and downstream seats, said magnetic means, at gas flow pressures above said second predetermined pressure, releasing said valve element for gas-flow induced movement into full seating contact with said downstream seat, and confining means surrounding said upstream seat and restricting radial displacement of said valve element adjacent said upstream seat in its movement between said fully seated and obliquely unseated positions.

6. The valve as claimed in claim 5 in which said valve element is a circular disk and said confining means is a substantially cylindrical cage having an inner diameter slightly greater than the outer diameter of said disk and enclosing both said seats.

7. A gas inhalation valve comprising a branched gas flow conduit extending between one inlet adapted to be connected to a source of gas under pressure and two outlets, a magnetically responsive valve element movable within said gas conduit between a pair of opposed upstream and downstream seats, said downstream seat being provided in one of said outlets, means for establishing a gas fiow from said source into said inlet at a first predetermined pressure, means for establishing gas flow into said inlet at a higher second predetermined pressure, and magnetic means adapted, at gas flow pressures below said first predetermined pressure, to hold said valve element in full seating contact with said upstream seat and, at gas flow pressures between said predetermined pressures, to hold said valve element in an obliquely unseated position in partial contact with said upstream seat, said magnetic means, at gas flow pressures above said second predetermined pressure, releasing said valve element for gas-flow induced movement into full seating contact with said downstream seat to close said one outlet.

8. The valve as claimed in claim 7 in which said magnetic means is adapted to yield a magnetic field which is asymmetric in relation to said upstream seat whereby said valve element in said obliquely unseated position will be biased towards a preferential direction of orientation in partial contact with said upstream seat within a predetermined zone on said seat.

9. A gas inhalation valve comprising a branched gas fiow conduit extending between one inlet adapted to be connected to a source of gas under pressure and two outlets, a magnetically responsive valve element movable within said gas conduit between a pair of opposed upstream and downstream seats, said upstream seat being provided in said inlet and the downstream seat being provided in one of said outlets, the other outlet being branched-off between said seats, means for establishing a gas fiow from said source into said inlet at a first predetermined pressure, means for establishing gas flow into said inlet at a higher second predetermined pressure, and magnetic means adapted, at gas flow pressures below said first predetermined pressure, to hold said valve element in full inlet-closing seating contact with said upstream seat and, at gas flow pressures between said predetermined pressures, to hold said valve element in an obliquely unseated position in partial contact with said upstream seat permitting gas flow from said inlet into both outlets, said magnetic means, at gas fiow pressures above said second predetermined pressure, releasing said valve element for gas-flow induced movement into full seating contact with said downstream seat to close said one outlet and divert the gas flow into said other outlet.

10. The valve as claimed in claim 9 in which said magnetic means is adapted to yield a magnetic field which is asymmetric in relation to said upstream seat whereby said valve element in said obliquely unseated position will be biased towards a preferential direction of orientation in partial contact with said upstream seat within a predetermined zone on said seat.

11. The valve as claimed in claim 9 in which said valve element is a circular disk, said seats are circular and said magnetic means is a substantially annular magnet surrounding said inlet upstreams of said upstream seat and having a gap at which the magnetic action is concentrated excentrically in relation to said upstream seat.

12. The valve as claimed in claim 9 in which said magnetic means is a single magnet disposed so as to yield an asymmetric magnetic field about said upstream seat.

13. The valve as claimed in claim 9 in which said magnetic means comprises a plurality of individual magnets disposed adjacent said upstream seat so as to yield an asymmetric magnetic field about said seat.

14. A medical treating unit comprising in combination a source of medical treating gas under pressure, a breathing mask, a valve having one inlet and two outlets, gas flow controlling means, and conduit means connecting said source to said valve inlet via said gas flow controlling means and connecting said breathing mask to one of said valve outlets, the other valve outlet being open to atmosphere, said valve comprising a magnetically responsive valve element movable within said valve between a pair of opposed upstream and downstream seats, said upstream seat being provided in said inlet and said downstream seat being provided in said outlet open to atmosphere, the outlet connected to said breathing mask being branched-off between said seats, said gas flow controlling means being adapted to establish a gas flow from said source into said inlet at a first predetermined pressure, said gas flow controlling means comprising pressure surge means actuatable to establish a gas flow into said inlet at a higher second predetermined pressure, and magnetic means adapted, at gas flow pressures below said first predetermined pressure, to hold said valve element in full inlet-closing seating contact with said upstream seat and, at gas flow pressures between said predetermined pressures, to hold said valve element in an obliquely unseated position in partial contact with said upstream seat permitting gas fiow from said inlet into both outlets, said magnetic means, at gas flow pressures above said second predetermined pressure, releasing said valve element for gas-flow induced movement into full seating contact with said downstream seat to close said one outlet open to atmosphere and to direct the gas flow through said other outlet into said breathing mask.

15. A resuscitation equipment comprising in combination means for supplying breathing gas under pressure, a breathing mask, a valve having one inlet and two outlets, and conduit means connecting said gas supply means to said valve inlet and said breathing mask to one of said valve outlets, the other valve outlet being open to atmosphere, said valve comprising a magnetically responsive valve element movable within said valve between a pair of opposed upstream and downstream seats, said upstream seat being provided in said inlet and said downstream seat being provided in said outlet open to atmosphere, the outlet connected to said breathing mask being branched-off between said seats, said gas supplying means comprising pressure surge means actuatable to establish a gas flow into said inlet at a pressure above a predetermined range of pressures, and magnetic means adapted, at gas flow pressures below said predetermined range, to hold said valve element in full inlet-closing seating contact with said upstream seat and, at gas pressures within said predetermined range, to hold said valve element in an obliquely unseated position in partial contact with'said upstream seat, said magnetic means upon actuation of said pressure surge means at pressures above said predetermined range releasing said valve element for gas-flow induced movement into full seating contact with said downstream seat to close said one out-let open to atmosphere and to direct the gas flow through said other outlet into said breathing mask.

References Cited by the Examiner UNITED STATES PATENTS 2,736,331 2/ 1956 Seeler 251--65 2,811,979 11/1957 Presnell 251-65 10 2,949,931 8/1960 Ruppright 251-65 

1. A GAS INHALATION VALVE COMPRISING A GAS FLOW CONDUIT OPEN AT OPPOSED ENDS, MEANS AT ONE OF SAID ENDS FOR CONNECTING SAID CONDUIT TO A SOURCE OF GAS UNDER PRESSURE, A MAGNETICALLY RESPONSIVE VALVE ELEMENT, MOVABLE WITHIN SAID CONDUIT BETWEEN A PAIR OF OPPOSED UPSTREAM AND DOWNSTREAM SEATS, MEANS FOR ESTABLISHING A GAS FLOW FROM SAID SOURCE TOWARDS SAID VALVE AT A FIRST PREDETERMINED PRESSURE, MEANS FOR TEMPORARILY ESTABLISHING GAS FLOW AT A SECOND PREDETERMINED PRESSURE HIGHER THAN SAID FIRST PREDETERMINED PRESSURE, AND MAGNETIC MEANS ADAPTED, AT GAS FLOW PRESSURES BELOW SAID FIRST PREDETERMINED PRESSURE, TO HOLD SAID VALVE ELEMENT IN INLET-CLOSING SEATING CONTACT WITH SAID UPSTREAM SEAT AND, AT GAS FLOW PRESSURES ABOVE SAID FIRST PREDETERMINED PRESSURE AND BELOW SAID SECOND PREDETERMINED PRESSURE TO HOLD SAID VALVE ELEMENT IN PARTIAL, INLET-OPENING CONTACT WITH SAID UPSTREAM SEAT, SAID MAGNETIC MEANS, AT GAS FLOW PRESSURES ABOVE SAID SECOND PREDETERMINED PRESSURE, RELEASING SAID VALVE ELEMENT FOR MOVEMENT INTO SEATING CONTACT WITH SAID DOWNSTREAM SEAT, 